THE INFLUENCE OF BITING FORCE ON THE STRAIN INDUCED WITHIN POSTERIOR ZIRCONIA THREE-UNIT FPD FABRICATED WITH TWO DIFFERENT VENEERING TECHNIQUES
Ebeid, Ahmed Kamal
El-Etreby, Amr S.
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Purpose: This study investigated the influence of biting force on the strain induced within posterior zirconia three-unit FPD fabricated with two different veneering techniques.Materials and Methods: Twenty 3-unit all ceramic zirconia bridges replacing missing upper second premolar were constructed and divided according to their veneering technique into two groups (n = 10/group). Group 1: Translucent Zirconia fabricated by fully anatomical technique (n=10), Group 2: Zirconia framework veneered by condensing and sintering VM9 low-fusing veneering porcelain by layering technique (n=10). The restorations were cemented on epoxy resin dies using dual cure adhesive resin Cement. Four KYOWA strain gauges (KYOWA, Tokyo, Japan) of 1 mm length were bonded, (1) at the cervical third (mesial margin) of the mesial wall of the 1st premolar retainer, (2) gingival surface of the Pontic, (3) buccal wall of the Pontic (below buccal cusp tip) and (4) at the cervical third of the distal surface of the 1st molar retainer using strain gauge cement (KYOWA, Tokyo, Japan). The samples were subjected to vertical loading (800 N) using universal testing machine.Results: Two-way analysis of variance (ANOVA), followed by Tukey’s post hoc test at a significance level of p≤0.05 was performed. There were significant differences between the two groups in the pontic and mesial sites while there were no significant differences found between the two groups in buccal and distal sites.Conclusions: Zirconia restorations resist vertical loading in a favorable and clinically acceptable mode. The strain induced in posterior three-unit zirconia restorations under normal biting force (800 N) has no catastrophic effect regardless of the technique of fabrication.
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